class_docstr: Keeps track of a running mean for seen states.
  
  The filter will be used to normalize observations and will be 
  online updated according to the seen observations of all actors.
code: def clear_buffer(self):
      self.buffer = RunningStat(self.shape)
  
imports: import numpy
label_desc: Use image node_id 2 for calling the MeanStdFilter obj's underlying member method code with example usage: obj.clear_buffer() without return types